UNIVERSITY OF SZEGED
Faculty of Science and Informatics
Doctorate School of Earth Sciences
Investigation of spatial and temporal changes of cave
climate in different karst areas of Hungary
Theses of dissertation
Beáta Csépe-Muladi
Supervisor
Dr. habil. László Mucsi
associate professor
Szeged
2016
1.
Introduction
“Cave climate is defined as the characteristic climate of a hole formed naturally in
solid rocks of the Earth’s crust” (Fodor, 1981). Cave air temperature usually
approaches the surface mean annual temperature and although there are seasonal
air exchanges between cave air and surface air with varying intensities, these
airflows do not hinder the formation of a characteristic cave climate. Cave
microclimate is also influenced by the features of cave entrances: height above sea
level, size, location (at valley bottom, hillside or hilltop), exposure and number.
Furthermore, passage morphology also affects cave microclimate, as passages of
different sizes and forms
react differently to the cave air circulation
(Stieber, 2014). Vegetation cover also influences cave air temperature conditions,
as due to shading under dense forests cave air temperature is more balanced
compared to open karsts (Zelinka, Stieber, 2014). Cave air temperature varies in a
cave system spatially, since the halls and corridors are not at the same elevation,
thus, an internal air circulation can start (Fodor, 1981). Apart from these
differences the cave is characterised by a more balanced climate compared to the
surface.
Cave air is continously exchanging with surface air due to the differencies in
their warming up, however, each cave has a different air circulation resulting in a
characteristic
cave
microclimate.
The
cave
climate
measurements
and
investigations significantly advance the knowledge on cave environments.
Due to climate change, being one of the most important environmental
problems, increasing climate extremities are current challenges on the surface
(drought years are followed by extreme humid years) and an important question
is how they influence the cave climate conditions.
The research on cave climate has a long history in Hungary. The first
measurements on the temperature of Stryx Creek were recorded in the Cave
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Baradla (Townson, 1797). In the report of Keresztély Raisz to Gömör County on
the Baradla Cave the temperature of the creek was also mentioned (Kessler, 1941).
For the end of the 19 th century an increasing number of researchers investigated
the formation, the development, the description and the classification of caves,
and there were growing number of studies including periodic temperature
measurements.
Based on the climate characteristics of cave entrance sections a general
classification was set up (Kordos, 1970): the first zone nearest to the entrance is
the cooling section in winter and the warming section in summer; the second and
the third ones are the turbulence and the warming sections, respectively.
In the book of István Fodor (1981) on cave climatology based on cave climate
investigations of Hungarian and foreign study areas, he classifies caves
considering human comfort. He analyses the climate conditions of the Baradla,
Abaliget, Tapolca and Telkibánya Caves, furthermore the Dobsina Ice Cave. His
complex cave climate investigations considerably advanced the development of
cave therapy as well. He grouped caves into 4 climate types in the aspect of cave
therapy considering human comfort as cold, cool, comfort and warm. There are
several other grouping possibilities of caves. Apart from the classification
speleometeorology demonstrated that as many caves exist, as many different subsurface microclimate can develop.
2.
Aims
The research addressed the following aims:
1. There has been an increasing attention on the preservation of cave environments
nowadays. To reach a more efficient prevention in the case of Rózsadomb thermal
karst a complex monitoring system was set up in 1995 in the Pál-völgyi Cave (in
the framework of the PHARE program), and climate measurements were also
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planned to include. The arrangement of the cables was time-consuming and
difficult with the given technical conditions (Bekey, 1995), and the system could
not operate due to the high humidity. By the technical development such
automatic wireless data recording systems were created, which can be placed in
the cave easily and can provide continuous data on the changes of cave climate. In
my doctoral research the applicability of a wireless sensor network
(UC Mote Mini) in cave environment, as methodological novelty, was tested.
2. The research addressed the mapping and the comparison of microclimate features
in caves of different genetics and morphology. Caves situated on three karst areas
were chosen as study areas: caves of hypogenic origin (the Pálvölgy Cave, the
Hideg-lyuk and the Harcsaszájú Cave in the Pálvölgyi cave system in Buda Hills),
a near-surface cave (the Hajnóczy Cave in Bükk Mountains) and a swallow cave
(the Trió Cave in Mecsek Mountains). In the investigated caves only periodic cave
climate and radon measurements were carried out, but temperature monitoring
networks were not set up.
3. The relationship between the elevation and the air temperature layering was also
investigated during my doctoral research (Muladi, Mucsi, 2013). Microclimatic
conditions were investigated on a cliff located at the entrance of Macocha Cave on
Moravian Karst in 2008 by Litschmann et al. (2012). The winter-summer
temperature profiles of the 138.4 m cliff showed seasonal temperature layering
and demonstrated how variable the temperature is depending on the height
above sea level. The air temperature rises with the rising elevation also in the
caves, however, the rate of increase is different (Fodor, 1981). Fodor investigated
the temperature layering in the Baradla-Domica Cave and found that the highest
vertical difference is at the entrance (0.4 °C in 140 cm). Bandino (2010) assessed
Italian caves and determined that the relationship is not linear between the
elevation and the temperature.
4. Three different sections can be separated in caves based on the distance from
the entrance: 0–2 m: cooling section in winter and warming section in summer;
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2–14 m: turbulence section; 6–14 m warming section, where cave air circulation
dominates (Kordos, 1970). The precise measurements allow this approach to be
reversed. Sections can be delineated based on the daily and annual temperature
fluctuation, and depending on the temperature variability, zones can be
allocated in distances from the entrance for each cave separately.
5. In my doctoral research the investigation of the temporal changes of cave air
temperature and the description of its long term (seasonal) changes were
addressed. Cave air temperature follows the periodical changes of surface
temperature in a different rate. The microclimate of the different cave sections
reacts to the changes of surface temperature differently on daily, seasonal and
annual levels, thus it informs about the temporal changes of air temperature
(Kordos 1970).
6. The favorable microclimate of caves allowed several utilization (Keveiné, 2009).
The measurement of cave climate parameters is important in the aspect of use as
well, as the visitors in caves, opened for tourists, influence cave climate
(Smith et al., 2013). The climate measurements can support tourism at National
Parks, as by their assessment optimal group size can be identified and surplus heat
can be avoided, which harms troglobion species. In actively explored caves for
research purposes the cavers can cause temperature anomalies due to the intensive
physical work for several hours. My aim was to determine the rate of aperiodical
changes in the studied caves, namely the rate of the anthropogenic influence due to
tourist groups visiting the cave and the rate of heat surplus caused by the research
activity of cavers. The assessment of the time, necessary for temperature and
humidity values to be restored to the original state following the cave visits, allows
the determination of the rate of cave ventilation. These data can be valuable for the
cave research, as they can also contribute to better understand the features of air
circulation of complex cave systems.
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3.
Applied methods
In parallel with the developing technology of wireless sensor network the number
of related applications was also increasing. The general features of the sensor
network are the short-range operation, the low cost and the low power
consumption. The nodes in the network are generally of small size and the
processor and the memory are limited. In case of wireless sensor networks the
application of expensive wired devices can be avoided, the devices can be easily
set up in the field and they communicate using radio communication. Extra
sensors can be integrated to the devices, thus more parameters can be measured
parallel (Lengyel, 2007).
The radio module of the UC Mote (using the IEEE 802.15.4/ZigBee wireless
communication protocol) can operate at a data rate of 250 Kbps in ISM 2.4 Ghz
band. The control is regulated by 16 MHz Atmel ATmega128RFA1 microprocessor
with 128 kB RAM. Several types of sensors are integrated as default into the
device: temperature, humidity and air pressure sensors. SHT21 measures
temperature and humidity, and MS5607-02BA03 records air pressure (Muladi et
al., 2012). The accuracy and the scale of SHT21 temperature and the humidity
sensor are ± 0.3 °C, 0.01 °C and ± 2.0% RH, 0.04% RH, respectively (Sensiron,
2011).
In the initial phase of the research the devices were tested in laboratory
environment, and the tests demonstrated that with adequate calibration the 0.3 °C
deviation between the devices can be eliminated. Preliminary measurements were
carried out in a climate chamber to provide exact calibration constants for each
sensor. Before the continuous measurements in the caves the sensors were tested
in the Hajnóczy Cave in the Bükk Mountains in December 2011 (the parameters
were measured in a 10-minute interval). During the research the number of study
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areas was continuously increasing. From April 2012 and April 2013 there were
continuous measurements in the Hideg-lyuk Cave and in the Pál-völgyi Cave (in
Buda Hills), respectively, and there were temporary measurements in the
Harcsaszájú Cave (being the member of the Pál-völgyi cave system) and in the
Trió Cave (in Western Mecsek karst area, Szuadó valley). 10 devices were placed
in both the Hideg-lyuk and the Hajnóczy Caves, where data were recorded in a
10 minute-interval, thus altogether 61.934 and 94.533 data from the two caves
were used for the assessment, respectively. 27 devices recorded 32.216 data from
the Pál-völgyi Cave providing information on caves closed from tourists. In case
of the Harcsaszájú and Trió Caves, 4.000 data were analysed.
The measured surface data were compared to the data of the nearest
meteorological stations in all cases. The recorded data at the Hajnóczy Cave was
compared to Szentlélek meteorological station. In the case of the Pál-völgyi,
Harcsaszájú and Hideg-lyuk caves the measured parameters of the meteorological
station at the Quarry were used. For the comparison in the case of the Trio Cave
the data of Pécs meteorological station were applied.
Polygon software was used for the spatial assessment of the caves and it
helped the planning and determination of device locations. The spatial distances
of the devices from the entrance were determined using this software as well.
The layout drawings of the caves were georeferred using ArcGIS software.
An overview 3D model was built using Therion software based on cave polygon
data and layout maps, and the model was clarified with cross sections.
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4.
Results
1. A new method was developed to investigate cave climate using UC Mote Mini
wireless sensor network.
Before the continuous temperature measurements in caves the applicability of the
devices was proved in both laboratory and cave environments. The 0.01 °C scale of
the sensors allowed the detection of slight temperature changes of natural and
anthropogenic origin.
The 0.3 °C difference in accuracy was eliminated by
calibration of the devices before the measurements. The devices can be easily and
rapidly installed and transported in the caves. High humidity was not problematic
for the sensors. Extreme underwater conditions in the caves resulted in data gaps,
however, these events did not cause damages in the devices. Using the new type of
wireless sensor network I successfully performed continuous data collection in
caves.
2. Based on the measured mean temperature the vertical cross section of
temperature distribution in the cave passages was performed.
The measured data confirmed that at the cave entrance sections temperature
layering can be observed due to the vertical differences. For example 10 °C
temperature difference was detected between the pit entrance and the deepest
explored point at the Áron Gábor 25 m long pit entrance in the case of the Hideglyuk Cave. Independently from height above sea level an increasing temperature
can be observed from the entrance towards the interior of the cave. Using the
measured mean temperature data of cave passages it was detected that the distance
from the entrance has higher influence on the temperature distribution than the
height above sea level.
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3. Entrance, turbulence and cave air circulation sections were delimited using
the daily, seasonal and annual fluctuation of the temperature and the distance
from the entrance.
Due to the convection air flow, cooling is observed in winter, while in summer
the air flows out from the investigated caves. The impact of surface conditions
on the caves are diverse, and the resulted changes in the cave passages have
different intensity. The categorization of the cave sections was carried out based
on long-term temperature measurements and seasonal observations. Different
intervals were given for each caves, as their entrances, the fracture system
connecting the surface, and the passage morphology caused different impacts.
Long-term measurements were carried out in two caves. In the Hajnóczy Cave
the entrance section is 14 m (ΔT=3.3–9.7 °C), the turbulence section is between
14 m and 64 m (ΔT=0.8–1 °C), than it is followed by the cave section (ΔT=0.1–
0.3 °C). In the Hideg-lyuk Cave the entrance section is 19 m (ΔT=4,4–13,6 °C), the
turbulence section is observed between 19 m and 48 m (ΔT=1,9–2,7 °C), and it is
followed by the cave section (ΔT=0,5–0,9 °C). The maximum temperature of the
airflow from the cave was also determined during summer air circulation, which
resulted in different values for the investigated caves (8.3 °C for the Hajnóczy
Cave and 9.4 °C for the Hideg-lyuk Cave). In the Pál-völgyi and Harcsaszájú
Caves the entrance zone was further classified according to the rate of surface
influence.
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4. The rate of seasonal and daily temperature fluctuations was determined in
different cave sections.
The seasonal temperature fluctuation assessments revealed the changes of the
airflow direction. Spring and autumn air circulations were short transitional
periods, when the temperature fluctuation is low in all section of the caves.
The assessment of the daily temperature fluctuation revealed what are the
atmospheric reasons for the temperature changes in the caves. I could allocate such
points in the caves where the air circulation is not through the entrance. The
thickness of soil and limestone layers above the passages was assessed to reveal if
the given fissure or fracture is permeable or not. The allocation of these points or
passage sections is of high importance for cave exploration. The cave measurements
allowed the detection of an airflow in a section of the Hideg-lyuk Cave, where
researchers explored a new 20 m long section of the cave in summer 2014 at a
formerly researched point.
5. The rate of anthropogenic influence was determined based on group and
passage sizes.
The former measurements of anthropogenic influence were carried out mainly in
show caves according to the literature. In the passages of the Hajnóczy Cave
characterized by diverse cross sections, the daily visitor groups of a summer
research camp were tracked by the measured temperature values. Based on these,
the heat surplus caused by the visitors in the different passage sections were
identified. My results highlighted that not only in narrow passages, but in wider
halls the positive temperature anomaly due to the visiting groups can be detected.
Beside the resulted temperature rise the relaxation time was also determined for all
passages. The heat surplus due to different visitor group sizes was investigated in
certain sections of the Trió Cave that is used only for overall cave visits.
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6. Complex air convection models were set up for all investigated caves based on
the impacts on the cave sections.
The assessment of the seasonal mean temperature and its fluctuation in the
different passage sections revealed that in what distance the inflowing air through
the entrance can modify the cave climate seasonally or where local temperature
anomalies can develop which cause specific air circulation. During summer air
circulation it was shown that air was flowing out of the caves through the entrance,
however, there were other cave sections where air inflow was detected (in the
Lapos Hall of the Hajnóczy Cave and in the sections of Medvecsapda and
Guillotine in the Hideg-lyuk Cave). These influences were indicated on the 3D
models and the heat maps of the caves.
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Publications in relation with the dissertation:
Muladi B., Csépe Z., Mucsi L., Puskás I. (2012): Application of wireless sensor
networks in Mecsek mountain’s caves In: Stünzi H.(Ed.): Proceedings of the 13th
National Congress of Speleology Zürich, Druckzentrum ETH-Zentrum, 131–136.
Muladi B., Csépe Z. (2013): Vezeték nélküli szenzorhálózatok egy barlangi
alkalmazási lehetősége Karszt és barlang 2011, I-II, 29–39.
Muladi B., Csépe Z., Mucsi L., Puskás I., Koltai G., Bauer M. (2013): Climatic features
of different karst caves in Hungary In: Michal Filippi, Pavel Bosák (Eds.) 16th
International Congress of Speleology: Proceedings, Prague, Czech Speleological
Society, 2, 432–438.
Muladi B., Csépe Z., Mucsi L. (2013): Barlangklimatológiai mérések két különböző
karsztterületen elhelyezkedő magyarországi barlangban In: Veress M. (ed.):
Karsztfejlődés, 18, 127–136.
Muladi B., Mucsi L. (2013): Látogató csoportok hatása a Trió-barlangban In: Galbács
Z. (ed.): The 19th International Simposium on Analytical and Environmental
Problems, 72–75.
Muladi B., Mucsi L. (2013): Investigation of Daily Natural and Rapid Human Effects
on the Air Temperature of The Hajnóczy Cave in Bükk Mountains Journal of
Environmental Geography, 6 (3-4),21–29.
Muladi B., Mucsi L. (2014): Investigation of the spatial and temporal trends of the air
temperature of the Hajnóczy cave in the Bükk mountains Geographica Pannonica,
18 (3). 51–61.
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